1. Field of the Invention
The present invention generally relates to metered dose inhalers (MDIs) and, more particularly, to the solubilization and delivery of polypeptides and proteins to the lungs.
2. Description of the Prior Art
A metered dose inhaler (MDI) typically comprises a canister under pressure fitted with a metering valve where the canister is filled with an aerosol formulation that includes a drug dissolved or dispersed in a propellant together with a surfactant. Nebulizers are devices which include a dry powder drug and a mechanical or electronic means to generate and deliver a fine mist of the drug. MDIs and nebulizers have been used for many years to treat pulmonary disorders such as asthma. Currently, several different types of drugs are routinely provided to patients using MDIs in the treatment of pulmonary disorders. Examples of these types of drugs include .beta.-agonists such as albuterol (salbutamol), isoproterenol, ephedrine, epinephrine, salmeterol, terbutaline, and norepinephrinec corticosteroids such as triamcinolone acetonide, beclomethasone diproprionate, dexamethasone, and aldosterone, allergic mediators such as cromolyn sodium, antibiotics, and anticholinergics. While the lungs have been recognized as a port to the bloodstream (e.g., through the lung mucosa), very little work has been performed in the area of using an MDI or nebulizer to deliver systemically active polypeptides or proteins to a patient.